Update build-unix.md
Update build-unix.md

Changed URL to clone to community repo
gridcoin/Gridcoin-Research,caraka/gridcoinresearch,Git-Jiro/Gridcoin-Research,theMarix/Gridcoin-Research,Git-Jiro/Gridcoin-Research,theMarix/Gridcoin-Research,Git-Jiro/Gridcoin-Research,gridcoin/Gridcoin-Research,caraka/gridcoinresearch,Git-Jiro/Gridcoin-Research,gridcoin/Gridcoin-Research,theMarix/Gridcoin-Research,caraka/gridcoinresearch,gridcoin/Gridcoin-Research,theMarix/Gridcoin-Research,theMarix/Gridcoin-Research,gridcoin/Gridcoin-Research,caraka/gridcoinresearch,theMarix/Gridcoin-Research,gridcoin/Gridcoin-Research,caraka/gridcoinresearch,Git-Jiro/Gridcoin-Research,caraka/gridcoinresearch